Gaming device manufactures have long provided gaming machines employing a plurality of reels, wherein the reels each have a plurality of symbols. In the 1930's, gaming device manufacturers provided a three reel gaming device, wherein each reel had ten stops, which produced a thousand combinations. One way for the manufacturers to increase the number of combinations was to increase the size of the reel and to add more stops. During the next four decades, the reels in the gaming devices increased to twenty stops. In the 1970's, manufacturers developed a twenty-two stop reel machine, in the early 80's a twenty-five stop reel machine, and in 1985, International Game Technology, the assignee of the present invention, developed a thirty-two stop reel machine. This machine had 32,768 possible combinations.
Another way manufacturers increased the number of combinations was to add reels. In 1955, a manufacturer produced a four-reel slot machine, which increased the number of combinations on a twenty stop machine to 160,000. In the middle 1970's, a manufacturer produced the first five-reel slot machine, which had twenty-two stop reels and produced combinations in excess of five million.
The next advancement in the effort to produce more payout combinations was the video or CRT screen slot machine, wherein the reels were simulated as opposed to mechanical. Video slot machines do not have mechanical drums or reels which rotate, do not need to precisely stop the same at certain positions and are therefore not limited by a maximum allowable drum radius. Each reel can have a virtuality unlimited number of stops. Initially, the Nevada gaming Commission limited the stops on the video machines (e.g., eighty-four stops on a three reel machine) but has since removed the limit. In 1989, a particular video reel machine employed reels having hundreds of stops and more than millions of combinations.
The total number of combinations affects the percentage of time that a player will obtain a particular winning combination as well as the overall payout percentage of the machine. For example, a three reel machine having twenty-two stops per reel, where the first reel has two oranges, the second reel has three oranges, and the third reel has seven oranges will yield an orange, orange and orange combination 42 times in every 10,648 plays (22×22×22) or 0.39% of the time. If the orange, orange, orange combination pays 20 coins, then the total coins paid is 20×42 or 840 coins in every 10,648 plays. Adding the total coins paid for each winning combination and dividing that number by 10,648 yields the machine's total payout percentage.
In the known gaming systems the percentage of obtaining a winning combination is set. In certain known progressive gaming machines, the payout of a grand prize grows each time a player plays the machine. The increasing payout increases the total coins paid as shown above, which in turn increases the overall payout percentage. Nevertheless, the percentage of times that a player will receive one of the combinations remains constant.
Free spins have also been provided in slot games. Upon winning free spins, the reels can auto-generate a number of outcomes and provide the player credits from winning symbol combinations occurring in the outcomes. Free spins provide an avenue for adding fun and excitement to standard gaming, while maintaining consistency with the slot base game and enabling the slot game to be played and displayed on simulated or electromechanical reels.
To increase player enjoyment and excitement, it is desirable to provide players with new types of gaming devices that attract the player and keep the player entertained.